Fig. 9

Schematic illustration and workflow of nanoparticle-based CRISPR-Cas system colorimetric gene detection. A Signal reporting is based on distance-dependent optical properties of the AuNP–DNA probe pair. In the presence of a target, linker ssDNA or ssRNA is degraded. The AuNP–DNA probe pair loses the hybridization linkers and becomes dispersed. In the absence of a target, linker ssDNA and linker ssRNA remain intact. Cross-linking reaction of the AuNP–DNA probe pair with linker ssDNA or ssRNA results in aggregation. B Workflow of CRISPR-based colorimetric gene detection. First, target DNA and RNA are added to Cas/crRNA complexes in the presence of linker ssDNA or ssRNA to prepare Solution 1. The AuNPs–DNA probe pair is mixed to prepare Solution 2. Subsequently, naked-eye detection can be completed by adding a drop of Solution 1 to Solution 2. (Reprinted with permission from [144])